Update #1: Significant Fuel Consumption Difference

[boscoe99]

Probably easier to remove in reverse. Put in reverse going about 45 mph and blow it all out the intake. Catch it in a towel to keep it tidy. Like blowing your nose.

Thanks for the graphic thought.

Remember the old days when men carried cloth handkerchiefs around with them. Using the same rag all day, nose blow after nose blow? No thanks.

[pstephens46]

Which way?

By running a motor at WOT in an over propped condition or by running a motor at WOT with no load at all? Or is it both?

Probably easier to remove in reverse. Put in reverse going about 45 mph and blow it all out the intake. Catch it in a towel to keep it tidy. Like blowing your nose.

[boscoe99]

Good to blow out the carbon from time to time.

Which way?

By running a motor at WOT in an over propped condition or by running a motor at WOT with no load at all? Or is it both?

[pstephens46]

Good to blow out the carbon from time to time.

[boscoe99]

why would anyone run a twin engine boat on one motor at WOT?

Damn if I know.

Sounds like the same kind of folk that will run a motor to WOT in neutral. Testing for something. I guess. Don't know what.

[99yam40]

why would anyone run a twin engine boat on one motor at WOT?

[bjd76]

Thx again for the interest and help. One other thing I forgot to mention is that we again did the single engine test to WOT. And similar to last time, the starboard engine went to 4100 rpm before prop slip/cavitation and Command Link showed about 25 gal/hr fuel consumption. The Port engine again went to 4600 rpm before prop slip/cavitation and showed about 21.7gph. Are the "codes" mentioned to be "input" and the results observed? Thx.

[rodbolt17]

actually the ECU does monitor the OCV's.
it is called intake cam timing and is displayed in degrees.
the ECU also monitors the port and stbd cam sensors .
were the throttle angles the same ?
you can use YDS to monitor that as well.
code 73 s-oil control valve
code 74 p-oil control valve.
your simply going to have to compare what the ECU's are seeing.

[boscoe99]

As rodnut has noted, injector pulse width varies based on a number of inputs to the ECU. For instance, engine temperature, air temperature, manifold pressure, throttle angle opening, etc..

When comparing pulse widths between two motors it might be a good idea to also see if the input variables are one and the same.

A quick swap of the ECU's might be performed just to see what can be seen when the ECU's themselves are the variable.

The oil control valve does not provide inputs to the ECU. The ECU simply tells them what to do. It does not monitor them to see if they are doing what is told.

Does your mechanic have a Yamaha "boat in the box"? This can be used to measure actual fuel flow to the motor to see how it compares with what the ECU is reporting as fuel flow. It is a conventional Yamaha fuel management meter that uses a sensor in the fuel hose to physically measure the rate of fuel flow.

[bjd76]

Thanks to all who offered advice/suggestions regarding my issue. I thought I would provide an update given that my mechanic has hooked up the PC to see what was going on. First thing we discovered is it is the starboard engine that is burning more fuel. When connecting the wire leads to the Command Link apparently someone had the starboard engine and fuel tank represented by the fuel gauge on the left! He analyzed both engines' plugs and saw 2 from the starboard engine that were worse than the others.

My installation of the new spark plugs were all ok.
With the new spark plugs in and the PC hooked up it

revealed that the starboard injectors were open longer - about 8.5 millisecs and the port injectors open 7.3millisecs (I think I have that right) at my normal cruise of 3600 rpm. We are going to replace the VST filters as start and take a trip and see how that does. If still a major difference he is thinking the injectors or injector screens may be a problem. He thought those scenarios may be more likely than a bad Oil Control Valve (OCV, which Yamaha calls an "oil solenoid if you're looking for it on their engine schematics). I have always bought fuel from the same gas station since I have owned the boat but fill tanks using 2 different hoses (therefore different dispenser filters). If dirty gas or tank bottoms I would have thought it would affect both engines but who knows...